Direct reduction processes for producing metallized iron from iron oxide pellets, lump ores, or similar materials which include iron oxide, are widely known and used in the steel industry. Suitable direct reduction processes for forming metallized iron are disclosed in U.S. Pat. Nos. 3,128,174 and 3,881,916. In a direct reduction process such as the Midrex Process, pellets of metal oxides are introduced at top of a shaft furnace to establish gravitational flow therethrough. Reducing gas consisting essentially of carbon monoxide and hydrogen is heated to sufficient temperature to effect direct reduction, is introduced to the metal oxide burden in the furnace, passes through the burden in counter-flow relation to the gravitationally descending burden, and reacts with the burden, forming metallized pellets and a reacted top gas consisting principally of carbon dioxide and water along with some unreacted reductants, which are drawn off as sulfur-containing spent top gas.
Additionally, U.S. Pat. No. 3,748,120 discloses a shaft furnace direct reduction process in which spent reduction gas is catalytically reformed from a mixture of gaseous hydrocarbon and spent reducing gas from the reduction process. In this process the spent reducing gas is cleaned and cooled upon exiting the reduction furnace and prior to being introduced into a catalyst-containing reformer. In the direct reduction process the reducing gas passes through and reacts with the burden to produce sulfur containing gases which contaminate the catalyst. Sulfur contamination of the catalyst lowers the overall efficiency of the process. Processes for reducing the sulfur level in the recycled spent reducing gas by increasing the metallic ion content of the scrub water utilized by the cooler-scrubber or by introducing a sulfur reducing agent into the spent reducing gas are also known. U.S. Pat. No. 4,019,441 teaches the introduction of a soluble salt into spent gas scrubber water.
By contrast with prior art processes, which require a specialized sulfur reducing agent, the present invention provides an improved method and apparatus for reducing the sulfur contamination of the gas reformer catalyst by selectively introducing into the scrub water insoluble process dust having an affinity for sulfur. The spent reducing gas interacts with the dust-laden scrub water, reducing the sulfur content of the recycled spent reducing gas, thereby reducing the sulfur contamination of the gas reformer catalyst.